1. Field of the Invention
The present invention relates to a recording apparatus and a recording method for recording information onto a plurality of information recording layers.
2. Description of the Related Art
Known as optical recording media for optically recording and/or replaying information are an optical disk, an optical card, etc. A semiconductor laser is used as a light source on the optical recording medium. A sharp laser beam, converged through a lens, is directed on the disk to record and/or replay information.
Techniques have been developed to increase recording capacity of such an optical recording medium. The effort to increase information recording density on a conventional optical disk focuses on increasing recording density on a disk recording surface. For example, a track pitch of the optical disk is narrowed in combination with the use of short wavelength of recording light and a signal process of a replay system. The information recording density in a linear direction is increased in a scan for recording and reading operations.
The use of the short wavelength of the light beam is limited to ultraviolet range. Even if an attempt is made to reduce the size of pits in the disk, the size is still limited to the size of the pit that is transferable to the disk in a cutting operation. The attempt to increase the recording density is thus expected to be subject to limitations at any rate in a two-dimensional region of the disk.
The capacity increasing technique is expanded to a three-dimensional structure. Multi-layer disks now draw attention. The multi-layer disk has information recording layers to increase information recording density in the direction of thickness thereof, draw attention.
A multi-layer recording medium with recording layers laminated thereon enables the recording capacity to be increased in accordance with the number of recording layers. A high-density recording medium is easily produced by combining the multi-layer technique with another high density recording technique. The multi-layer recording media are already commercially available as a digital versatile disk (DVD)-ROM as a read-only optical disk.
For example, U.S. Pat. No. 6,061,310 and U.S. Pat. No. 6,330,212 disclose techniques that are applicable to a two-layer structure in a DVD-ROM.
The development and use of a multi-layer recording medium having laminated recording layers made of a recording material such as a phase change material, a magneto-optical material, or a dye material are expected in addition to the ROM type disk. For example, the employment of multi-layers is expected in the DVD-type disks including write-once-type disks called DVD−R and DVD+R, and rewritable-type disks called DVD−RW and DVD+RW.
In the multi-layer recording medium, layer shifting is performed during a recording operation. In the case of two layers, for example, data recording is performed first on a first layer (layer 0), and continuously performed on a second layer (layer 1). If consecutive pieces of user data are recorded straddling across layer 0 and layer 1, replay of the data from layer 1 is subject to a problem. FIG. 14 illustrates this problem.
As shown, a series of user data DA1-DA8 is consecutively recorded across two layers of layer 0 and layer 1.
User data recording starts with user data DA1 on layer 0. When the recording area of layer 0 is fully used with data DA6 recorded, data recording resumes on layer 1 to record the remaining data DA7 and DA8.
It is now assumed that predetermined regions, such as a lead-in zone, a lead-out zone, and a middle area (all to be discussed later), are not formed yet. For example, in the write-once type disk, these regions are formed in a disk close (session close) process or a finalize process. FIG. 14 illustrates the disk that has undergone only user data writing prior to the disk close process.
The user data is now replayed under the state shown in FIG. 14.
When the close process is performed subsequent to the user data recording, management information based on the user data recorded on the disk is typically recorded and required regions are formed in the write-once disk and the rewritable disk. The disk is thus normally replayed on a replay only apparatus. Even in the state shown in FIG. 14, a recording apparatus that has recorded the data can replay the data. More specifically, the recording apparatus itself has recorded the data, and naturally holds information corresponding to the management information to be recorded in succession, and thus knows an address bearing the recorded user data.
The recording and replay apparatus having the user data recorded as shown in FIG. 14 may unload the disk with no close process performed taking into consideration additional recording. In such a case, management information corresponding to the user data recorded up to this point of time is recorded in a predetermined area of the disk, although this process is not the close process. A recording and replay apparatus compatible with such an unclosed disk can replay the user data from the unclosed disk with the user data recorded.
When such an unclosed disk is replayed, the replaying of layer 1 cannot be performed if the user data is recorded straddling across layer 0 and layer 1.
As shown in FIG. 14, data DA7 is recorded on layer 1 in succession to data DA6. During the replaying of the data DA7, a pickup of the apparatus accesses a head portion of the data DA7 in the layer 1, and starts replaying toward inner circles. An area immediately ahead of the data DA7 is in an unrecorded state. For a duration of time up to the head portion of the data DA7, no replay signal is available. In other words, only when the pickup reaches the head portion of the data DA7 in an access operation, a replay signal is obtained.
To be ready for replaying, the gain of a replay signal obtained from a reflected light beam is adjusted, a synchronization process for decoding the replay signal is performed, and PLL looping for generating a replay clock is performed. Only after these pre-replay processes, the replay signal is decoded. The pre-replay process cannot be performed without any replay signal.
If the replaying of the data DA7 in layer 1 is attempted, the replay signal is obtained when the pickup reaches the head portion of the data DA7. At this point of time, the pre-replay process is enabled. When the decoding operation is possible, the replay operation of the pickup is in progress finishing the head portion of the data DA7. The head portion of the data DA7 thus ends without being decoded.
For this reason, the user data of layer 1 cannot be appropriately replayed.
A guard block (not shown) for recording dummy data is typically formed prior to the start of the data recording.
As shown in FIG. 14, dummy data is recorded starting in a circle slightly inner than the head portion of the data DA1 when the data recording of the data DA1 starts in layer 0. Subsequent to the recording of the dummy data, the user data of the data DA1 is recorded. When the data DA1 is replayed in layer 0, a replay signal is obtained from the guard block of the dummy data, thereby allowing the pre-replay processes to be performed. The replay operation of the data DA1 is appropriately performed.
When a series of user data of data DA1 through DA8 is recorded on layer 1, a guard block is formed immediately ahead of the recording of the data DA1, and no problems take place in the replay operation.
A problem takes place in the replay operation when layer shifting is performed during the recording of a series of data, and when the user data has an unrecorded region immediately ahead thereof in a destination recording layer.